The prior art is already aware of various arrangements of supports or safety devices for upwardly supporting pivotal members, such as vehicle lifts and other types of lifting and hoisting member. Examples of prior art supports, utilized in connection with fluid power, such as fluid cylinder assemblies, are found in U.S. Pat. Nos. 2,550,764 and 3,223,251 and 3,317,004 and 3,330,381. These prior art devices show utilization of a pivotally mounted support member which can be positioned between two abutment surfaces when a fluid cylinder assembly has been extended, and thus the support member retains the extended position even though the fluid is exhausted in the cylinder assembly.
However, the present invention relates to a boom arm safety lock wherein the arrangement is made for upwardly supporting a boom arm, such as one which is utilized on a tractor and has a material-handling bucket or the like on the extending end of the arm. In these instances, it is significant that the apparatus is arranged so that a support member or lock bar can be readily and easily positioned in a safe and supportive position for the boom arm when the arm is in the upwardly pivoted position. Further, in this arrangement, support member or lock bar is under the control of the operator who is normally seated on a tractor or the like and can reach the support member or lock bar to position it in its supporting position, and the arrangement is such that the support member or lock bar will also be retained in an inoperative position and will not interfere with the normal operation of the boom arm and cylinder assembly, and the support member or lock bar need not be maneuvered unless and until the supported position is desired. Accordingly, the present invention provides a boom arm safety lock which is simplified in its structure and arrangement and which is completely reliable for supporting the weighty boom and which is readily accessible to the operator for positioning in the operative position and also for retracting the support member from the operative position and placing it into a secured inoperative position.
In considering the foregoing, it will also be understood that the tractor and the boom arm commonly require that the boom arm be left in a raised position while the operator removes himself from the location of the controls for the fluid cylinder assembly and the like, and at that time the operator may be required to inspect the work area or service the boom arm in the way of greasing or checking hose connections or the like. At those times, it is important that the boom arm be in a safe position and secured in that raised position so that there will be no personal injury or property damage. As such, the present invention provides an arrangement for a support member or lock bar which actually positions itself in the securing mode, at least once the operator has released the lock bar so that it is available for securing the boom arm in the raised position.